Regulating the phase separation of ternary organic solar cells via 3D architectured AIE molecules

An optimized bulk heterojunction (BHJ) interface, certifying enhanced exciton-splitting, charge separation and recombination inhibition, is vastly desired to obtain high power conversion efficiencies (PCEs). Herein, the ternary strategy has been employed to effectively modify the phase separation between the J71:ITIC blend by incorporating a 3D aggregation-induced emission (AIE) material, Tetraphenylethylene (TPE). Hence, as a consequence of improved charge mobility, lower bimolecular recombination and enhanced fill factor (FF), an excellent PCE of 12.16% has been achieved; a 21.23% increment over the PCE of binary devices. Likewise, Flory-Huggins parameter (chi) and surface free energy analysis reveals a high degree of miscibility between J71 and TPE, that leads to a rearrangement at the D-A interface such that TPE settles in between the D and A and thus forces the ITIC away from J71 and out of the mixed phase, indicating relatively higher average acceptor domain purity at the interface and ultimately better FF and PCE for the ternary devices. Likewise, the TPE inclusion in various other fullerene and nonfullerene systems also led to similar results, signifying this to be an effective methodology to boost the PCEs of the organic solar cells, especially for the systems with low FF.